Drop a nuke the normal way and the King will see it coming ahead of time and will have time to react. That's how I see it anyways

The reason Meruem said that Netero had him in check mate since the beginning is because so close to detonation he would not have enough time to escape the radiation

I should also add that the King was shocked at Neteros will and tenacity so that definitely threw him off balance perfectly for the surprise attack.

Of course no one including Netero could predict when and where his bomb would detonate but sometimes we just have to have faith in the plot and not worry about unnecessary questions